Modern radio access technologies, such as Long Term Evolution (LTE), use Orthogonal Frequency Division Multiple Access (OFDMA) modulation schemes to overcome Inter-Symbol Interference (ISI) caused by multipath fading. OFDMA implements orthogonal spaced sub-carrier signals and inserts a cyclic prefix (CP) as a guard interval to eliminate ISI. To compensate for distortion resulting from the propagation of transmission of the signal through communication channels, the user equipment (UE) is required to perform channel estimation (CE) to increase capacity and allowing for proper signal detection and data demodulation. The more accurate the CE, the better the receiver is able to receive data from the transmitter.
To facilitate CE, LTE uses reference signals consisting of pilot symbols in the time and frequency domains to provide an estimate of the channel at given locations within a subframe. The pilot symbols are used to provide a reliable estimate of the complex gains of each resource element of signal transmission through the communication channel. Using the known pilot symbols to estimate the channel, the UE may equalize the effects of the communication channel and reduce the noise on the received signals.
Data aided CE improves the quality of CE by using data symbols acquired from the data signals in CE. The additional information gained from the estimated data is used in conjunction with information received from the reference signal in order to provide a more accurate CE. However, current CE methods, even data aided CE methods, do not provide good performance in conditions of special interest in mm-waves communications and in high Doppler scenarios.